Our FAQ
covers all sorts of topics, including questions about setting up a client
or relay, concerns about anonymity attacks, why we didn't build Tor in
other ways, etc.
There's a separate Abuse FAQ to answer
common questions from or for relay operators.
The Tor Legal FAQ is written by
EFF lawyers, and aims to give you an overview of some of the legal issues
that arise from The Tor Project in the US.

If you have questions, we have an IRC channel (for users, relay
operators, and developers)
at #tor on irc.oftc.net. If
you have a bug, especially a crash bug, read how
to report a Tor bug first and then tell us as much information
about it as you can in
our bugtracker.
(If your bug is
with your browser or some other application, please don't put
it in our bugtracker.) The
tor-talk mailing list can also be useful.

Tor has a blog.
We try to keep it updated every week or two with the latest news.

Download and watch Roger's Tor
overview talk from Internet Days in Sweden (video,
slides,
youtube),
which provides good background on how Tor works and what it's for.

Our sponsor TODO list starts with a
timeline for external promises — things our
sponsors have paid to see done. It also lists many other tasks
and topics we'd like to tackle next.

Once you're up to speed, things will continue to change surprisingly fast.
The tor-dev mailing list is where the complex
discussion happens, and the #tor and #tor-dev IRC channels
are where the rest of the discussion happens.

Our preliminary design to make it harder for large firewalls to
prevent access to the Tor network is described in
design of a blocking-resistant anonymity system:
PDF draft and
HTML draft.
Want to help us build it?

The specifications aim to give
developers enough information to build a compatible version of Tor:

Check out Tor network status information using Relay Search.
Remember that these lists may not be as accurate as what your Tor
client uses, because your client fetches its own directory information and
examines it locally.

Read these
papers (especially the ones in boxes) to get up to speed on the field
of anonymous communication systems.